I would recommend Connaught no wash basin as #1 as you'll be in old quad which has HUGE rooms. But then I'm biased. Great social life, very sociable, not problems with sharing bathrooms.
My friend was in Monte 2 and hated it. Room was small and not very sociable. She transferred to GE, not sure which one and much prefers it. Don't think that there's a lot of difference between RN and CC but then I don't live there.

I'm in Monte 2. Not bad but definately not the best. Rooms vary in size a lot and walls are ridiculously thin. Rooms in each flat are numbered A-G and B and F are the smallest. Room B has the communal shower built in it so that takes up a lot of room and F has the communal toilet in it. With thin walls you can here people take a dump, piss or shower if you're in rooms B or F.

I can whole-heartedly recommend Chancellors' Courts. RN's alright, but the decor and fixtures are over 10 years old now, and starting to show it. Chancellors' is still in great condition, the rooms are only slightly smaller than the Connaught Old Quad ones, and I cannot over-emphasise the benefits of having a double bed. But either way there's the (very excellent) Glen JCR.

But if you've selected Small Halls as your first choice you're very likely to get it, seeing how few apply for it as their first. The majority who don't get their first choice are those who select en-suite at Glen or Monte and end up at Orion's Point. Trust me. I've seen the stats.

I was in Montefiore 2 and absolutely loved it! The social side of things there was great and although the halls themselves weren't amazing, the time you will have there will be so much fun. I can't speak for Glen Eyre, but friends who lived there also loved it. Ultimately, I don't think it matters too much which halls you get put in, as it's what you make of it and the friends you end up living with that counts! I'm sure you will enjoy wherever it is you end up

If you want more information on what it's like living in the halls at Southampton you can find interviews with students who have lived there at: http://southamptonsas.wordpress.com/